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Old 01-09-2023, 07:32   #1
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Iron keel rusting; what's the best epoxy?

My 2009 Beneteau 343 has had a good history in terms of bottom paint performance (at least 3 years each job) but recently it seems some primer and paint have let go at top of keel portside where it meets the hull. I had growth in this area so I scraped it off. I think the paint came with it. It is a 1.5 year bottom job using Ultra Interlux.

I guess I will need to haul, sand to bear metal, apply a couple layers of epoxy, primer, and paint. My questions are:
What's the best epoxy to use on an iron keel?
It isn't a huge spot; how much of the keel do I need to expose to ensure good adhesion of the epoxy?
Is it possible that I might have too many coats of paint on keel? I get 3 coats about every 3 years and I haven't sandblasted hull in a long time.

Thanks
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Old 03-09-2023, 16:45   #2
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Re: Iron keel rusting; what's the best epoxy?

Regardless of brand of epoxy, I would review notes from the West System websites.

Repairing a Keel with G/flex Epoxy
https://www.epoxyworks.com/index.php...h-gflex-epoxy/

Surface Preparation | WEST SYSTEM Epoxy
https://www.westsystem.com/instructi...e-preparation/

I read through the two above links and called West Technical support to ask specific questions. I settled on a modified set of their instructions taking into account the heavier wet film thickness I got with my epoxy and the parts being off the boat and lying flat on furniture dollies:

-sanded cast iron to bare metal w/ poly-carbide disks
-applied epoxy (2:1 non-blush), rubbing it wet into metal with a wire brush
-next day, repeat with epoxy+411 barrier powder w/o wire brushing
-let fully cure minimum 1 week, sand to 60 grit
-applied my choice of bottom paint

I am waiting for last minute touch-ups of epoxy + barrier powder to cure on the hull before bolting back together with a layer of 5200 between fiberglass hull and external keel stub.

All the best!
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Old 03-09-2023, 18:18   #3
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Re: Iron keel rusting; what's the best epoxy?

With cast iron, the success of the bottom layer is ALL about surface prep. It needs to be blasted or ground down to bright silver metal. ALL bright. No trace of anything else. Then IMMEDIATELY, not tomorrow morning, but within four hours... sooner if possible, get the first sealing layer on before a micro layer of rust can develop. If you are paying somebody to do this, MAKE SURE this is what happens.

When cleaning the surface after grinding or blasting do NOT use paper or fabric towels to wipe it down! Fibers get caught on the little metal hooks on the surface, and those fibers act like wicks to pull water down to the metal surface, guaranteeing quick failure of the coating. Even if you are dealing with a professional painter you trust, it's 100% on YOU to read the instructions, understand them, and make sure they are followed exactly. No shortcuts.

If done right and with good attention to detail, the base finish can easily last a decade, or even two. If wrong, it will be coming off in a season or two.
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Old 03-09-2023, 18:40   #4
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Re: Iron keel rusting; what's the best epoxy?

Quote:
Originally Posted by SailingHarmonie View Post
With cast iron, the success of the bottom layer is ALL about surface prep. It needs to be blasted or ground down to bright silver metal. ALL bright. No trace of anything else. Then IMMEDIATELY, not tomorrow morning, but within four hours... sooner if possible, get the first sealing layer on before a micro layer of rust can develop. If you are paying somebody to do this, MAKE SURE this is what happens.

When cleaning the surface after grinding or blasting do NOT use paper or fabric towels to wipe it down! Fibers get caught on the little metal hooks on the surface, and those fibers act like wicks to pull water down to the metal surface, guaranteeing quick failure of the coating. Even if you are dealing with a professional painter you trust, it's 100% on YOU to read the instructions, understand them, and make sure they are followed exactly. No shortcuts.

If done right and with good attention to detail, the base finish can easily last a decade, or even two. If wrong, it will be coming off in a season or two.

I would add….not only epoxy quickly after prepping….use a cheap wire brush to forcefully brush the epoxy into the metal while it is still fluid. So any micro rust layer is obliterated and cannot reform, as the epoxy now blocks any air from reaching the newly abraded metal. Toss the used brush when done.

I did this once on some leaking aluminum fuel tanks and it worked…..held diesel for years until I sold the boat.
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Old 03-09-2023, 19:16   #5
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Re: Iron keel rusting; what's the best epoxy?

PS 422 not 411 for the West # of the barrier coat additive

https://www.westsystem.com/product-c...ies/additives/
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Old 03-09-2023, 19:32   #6
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Re: Iron keel rusting; what's the best epoxy?

Or you use por15: https://por15.com/
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Old 04-09-2023, 01:03   #7
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Re: Iron keel rusting; what's the best epoxy?

1/Sand the top surface of the keel untill you reach clean, unoxidised metal
2/Wipe away any dust or grease using Acetone
3/KIM TEC Zinkstaub farbe (or any good Zinc Dust Paint you find on your market for offshore use ), paint the keel
4/other coating what depend antifouling you use, 4-6 layer or more + 2-3 antifouling
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Old 04-09-2023, 04:02   #8
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Re: Iron keel rusting; what's the best epoxy?

I definitely agree you should get the epoxy on quickly after blasting, use compressed air to remove the media after blasting rather than any wiping.

The step I would add is that since you have an iron keel, you can and should holiday test! Whichever epoxy you pick, the tech data sheet may specify what type of test. But typically thickness<20mils wet sponge thickness>20mils spark test. You might have to borrow the equipment, the testers will be in the 1-3k range.
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Old 04-09-2023, 04:29   #9
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Re: Iron keel rusting; what's the best epoxy?

Quote:
Originally Posted by SailingHarmonie View Post
With cast iron, the success of the bottom layer is ALL about surface prep. It needs to be blasted or ground down to bright silver metal. ALL bright. No trace of anything else. Then IMMEDIATELY, not tomorrow morning, but within four hours... sooner if possible, get the first sealing layer on before a micro layer of rust can develop. If you are paying somebody to do this, MAKE SURE this is what happens.

When cleaning the surface after grinding or blasting do NOT use paper or fabric towels to wipe it down! Fibers get caught on the little metal hooks on the surface, and those fibers act like wicks to pull water down to the metal surface, guaranteeing quick failure of the coating. Even if you are dealing with a professional painter you trust, it's 100% on YOU to read the instructions, understand them, and make sure they are followed exactly. No shortcuts.

If done right and with good attention to detail, the base finish can easily last a decade, or even two. If wrong, it will be coming off in a season or two.

This is true 100%..
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Old 26-10-2023, 01:44   #10
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Re: Iron keel rusting; what's the best epoxy?

For addressing rusting on an iron keel, using an epoxy barrier coat is a wise choice. You can consider well-regarded epoxy products such as alodine 1200s for this purpose. These are known for their excellent adhesion and protective qualities.
To ensure good adhesion of the epoxy, it's generally recommended to expose the affected area down to clean, bare metal. This allows the epoxy to bond properly and provide effective corrosion protection.
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Old 26-10-2023, 06:50   #11
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Re: Iron keel rusting; what's the best epoxy?

Quote:
Originally Posted by IslaMujeres View Post
For addressing rusting on an iron keel, using an epoxy barrier coat is a wise choice. You can consider well-regarded epoxy products such as alodine 1200s for this purpose. These are known for their excellent adhesion and protective qualities.
To ensure good adhesion of the epoxy, it's generally recommended to expose the affected area down to clean, bare metal. This allows the epoxy to bond properly and provide effective corrosion protection.
And I used Osho on the bare metal before we put down e-flex and another, harder, epoxy to repair the damaged keel.
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